KatePart

KatePart is a fast and feature-rich text editor component with many advanced features. It implements the KTextEditor interfaces, a common interface collection for text editor components in KDE, allowing it to be selected as the editor in applications that lets the user chose from different implementations, and it can use KTextEditor plug-ins.

KatePart is originally based on code from the KDE 1 richtext editor widget, but has been almost completely rewritten over the years. It is the default text editor widget in Kate and KWrite and also the default to display text in Konqueror. A lot of other applications use it as text editing component, too, like KDevelop.

Features include

Syntax highlighting for more than 180 text formats, including popular programming languages like C/C++, Java, Ruby as well as markup such as HTML and XML.